1. Field of the Invention
The present invention relates to selected 3-trichloromethyl-5-cyclic amine-1,2,4-thiadiazole compounds as compositions of matter. Furthermore, the present invention relates to nitrogenous fertilizer compositions containing one or more of these compounds. Still further, the present invention relates to the use of these compounds to inhibit the nitrification of ammonium nitrogen present in the soil.
2. Description of the Prior Art
The use of nitrogenous fertilizers (e.g., liquid ammonia, urea, ammonium salts such as ammonium sulfate, ammonium nitrate and ammonium phosphate, and the like) to improve plant nutrition and growth is well-known. These nitrogenous fertilizers, upon addition to the soil, from ammonium ions, which act as a suitable nitrogen source for cultivated crops. Specifically, because these ammonium ions are generally adsorbed and retained by clay and decomposing vegetation in the soil, they remain readily available for plant utilization.
However, through the bacterial process of nitrification, ammonium ions are converted to nitrates. Although nitrates are beneficial in some situations, they have, as anions not bound to soil colloids, the undesirable characteristic of being washed or leached away easily by rain or irrigation. Thus, situations where relatively rapid nitrification of the ammonium ions is accompanied by rain or irrigation may cause a great waste of fertilizer.
To be more specific, nitrification is the process whereby ammonium-nitrogen is converted to nitrite-nitrogen and then nitrate-nitrogen. This oxidation is carried out by various microorganisms called nitrifiers as illustrated by the following sequence: ##STR1## The addition of chemical agents to the soil in order to inhibit or suppress the nitrification process and, thus, retain the nitrogen in the cationic ammonium form in the soil is well known. Such chemical agents are generally called nitrificides or nitrification inhibitors. These chemicals are toxic to the microorganism nitrifiers and will slow down or completely block the oxidation of ammonium ions to nitrates in the soil. More specifically, it is known that there are three types of nitrification inhibitors, namely, ammonium nitrification inhibitors; nitrite nitrification inhibitors; and ammonium-nitrite nitrification inhibitors. Ammonium nitrification inhibitors have been found to be the most commercially important of the three types because they have a positive effect, as compared to the other two types, on the nitrogen balance of soils and of many plants. See Sommer, K. Nitrificides, Landwirt. Forsch. Sonderh. Volume 27, pages 64-82 (1972) for a more detailed discussion of these three types of inhibitors.
In particular, it was pointed out in this article by Sommer that 3-trichloromethyl-5-ethoxy-1,2,4-thiadiazole is a very effective ammonium nitrification inhibitor. Besides having this beneficial activity, it was known that this compound is a soil fungicide. See U.S. Pat. No. 3,260,725, which issued to H. A. Schroeder on July 12, 1966. Consequently, the use of this particular compound in the soil has a valuable double action. This compound, however, has one shortcoming as a nitrification inhibitor, namely, that it is unstable in liquid ammonia solutions. Accordingly, it can not be applied as a nitrification inhibitor to the soil in the increasingly more popular liquid ammonia solutions.
Another recent development in the employment of other 1,2,4-thiadiazole compounds as nitrification inhibitors was disclosed in Japanese Patent Publication No. 4962/72, published Feb. 12, 1972, wherein it was taught that selected 3-trichloromethyl-5-non-cyclic amine-1,2,4-thiadiazoles may be used as nitrification inhibitors. However, as shown in the comparison examples cited in Table 4, below, the nitrification-inhibiting activity of these prior art compounds at the commercially-used amounts of 1.0 part per million parts by weight of soil is generally unsatisfactory.
Accordingly, it is believed that there still exists a need in this art for ammonium nitrification inhibitors which have a commercially suitable activity while being soluble and stable in liquid ammonia fertilizers. Furthermore, it would be highly desirable if such chemicals also had a relatively low vapor pressure so they would not vaporize readily into the atmosphere; not be easily washed away from soil by water; be non-toxic to man, livestock and plants; and, finally, be relatively inexpensive. It is believed that compounds within the scope of the present invention have all of these desirable characteristics.